drivers: sensor: SHT4X Added support

This adds support for Sensirion's SHT4X temperature and
humidity sensor.

Signed-off-by: Leonard Pollak <leonardp@tr-host.de>

include/drivers/sensor/sht4x.h

@@ -0,0 +1,50 @@
+/*
+ * Copyright (c) 2021, Leonard Pollak
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @file
+ * @brief Extended public API for Sensirion's SHT4X T/RH sensors
+ *
+ * This exposes an API to the on-chip heater which is specific to
+ * the application/environment and cannot be expressed within the
+ * sensor driver abstraction.
+ */
+
+#ifndef ZEPHYR_INCLUDE_DRIVERS_SENSOR_SHT4X_H_
+#define ZEPHYR_INCLUDE_DRIVERS_SENSOR_SHT4X_H_
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <drivers/sensor.h>
+
+/* Maximum teperature above which the heater should not be used */
+#define SHT4X_HEATER_MAX_TEMP 65
+
+enum sensor_attribute_sht4x {
+	/* Heater Power: 0, 1, 2 -> high, med, low */
+	SENSOR_ATTR_SHT4X_HEATER_POWER = SENSOR_ATTR_PRIV_START,
+	/* Heater Duration: 0, 1 -> long, short */
+	SENSOR_ATTR_SHT4X_HEATER_DURATION
+};
+
+/**
+ * @brief Fetches data using the on-chip heater.
+ *
+ * Measurement is always done with "high" repeatability.
+ *
+ * @param dev Pointer to the sensor device
+ *
+ * @return 0 if successful, negative errno code if failure.
+ */
+int sht4x_fetch_with_heater(const struct device *dev);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* ZEPHYR_INCLUDE_DRIVERS_SENSOR_SHT4X_H_ */